During the academic year 2015-2016, I organized the weekly seminar Groups, Actions and von Neumann algebras at the Université Paris-Sud, Orsay. This seminar featured both research and introductory talks.

#### Meetings

##### Thursday October 8

Amaury Freslon (Université Paris-Sud)

*Introduction to C*-simplicity for discrete groups*

##### Thursday October 22

Amine Marrakchi (ENS Paris and Université Paris-Sud)

*Furstenberg and Hamana boundaries of discrete groups (Part I)*

##### Thursday November 12

Amine Marrakchi (ENS Paris and Université Paris-Sud)

*Furstenberg and Hamana boundaries of discrete groups (Part II)*

Cyril Houdayer (Université Paris-Sud)

*C*-simplicity and the unique trace property for discrete groups (after Breuillard-Kalantar-Kennedy-Ozawa) (Part I)*

##### Thursday November 19

Cyril Houdayer (Université Paris-Sud)

*C*-simplicity and the unique trace property for discrete groups (after Breuillard-Kalantar-Kennedy-Ozawa) (Part II)*

##### Thursday November 26

Arnaud Brothier (Vanderbilt University)

*Approximation properties and subfactors*

##### Thursday December 3

Yves de Cornulier (CNRS and Université Paris-Sud)

*Groups of tree automorphisms with an almost everywhere prescribed action*

##### Thursday December 17

Yuhei Suzuki (The University of Tokyo)

*Minimal ambient nuclear C*-algebras*

##### Thursday January 7

Cyril Houdayer (Université Paris-Sud)

*Bi-exact groups, strongly ergodic actions and group measure space type III factors with no central sequence*

##### Thursday January 21

Romain Tessera (CNRS and Université Paris-Sud)

*A functional analysis proof of Gromov’s polynomial growth theorem (after Ozawa) (Part I)*

##### Monday January 25

Romain Tessera (CNRS and Université Paris-Sud)

*A functional analysis proof of Gromov’s polynomial growth theorem (after Ozawa) (Part II)*

##### Monday February 1

Jean Lécureux (Université Paris-Sud)

*Bader-Shalom’s normal subgroup theorem (Part I)*

##### Monday February 8

Jean Lécureux (Université Paris-Sud)

*Bader-Shalom’s normal subgroup theorem (Part II)*

##### Monday February 29

Koichi Shimada (The University of Tokyo)

*Examples of maximal amenable subalgebras in free group factors arising from irrational rotation algebras*

##### Monday March 14

Rémi Boutonnet (CNRS and Institut de Mathématiques de Bordeaux)

*II_1 factors with non-isomorphic ultrapowers*

##### Monday March 21

Sven Raum (WWU Münster)

*C*-simple and non-C*-simple locally compact groups*

##### Monday April 4

Camille Horbez (CNRS and Université Paris-Sud)

*An introduction to Out(Fn)*

##### Monday April 11

Camille Horbez (CNRS and Université Paris-Sud)

*The Poisson boundary of Out(Fn)*

##### Monday June 20

Hiroshi Ando (Chiba University)

*Unitarizability, Maurey-Nikishin factorization and Polish groups of finite type*